Final answer:
The laddering technique is the approach used to ask respondents to compare differences between brands at different levels, helping to uncover motivations behind preferences.
Step-by-step explanation:
The probing approach that asks respondents to compare differences between brands at different levels is known as laddering. The laddering technique involves asking respondents to explain why they prefer one brand over another, which can uncover the attributes, consequences, and personal values that lead them to choose one product or service over another. This method helps to identify the underlying motivation behind customer choices and preferences.
The options 'interrogating' and 'elaborating' do not specifically pertain to comparison between brands, while 'linking' is not commonly used in the context of probing questions in marketing research. Other options, such as 'interrogating' may seem plausible because it implies a deep or thorough questioning process, but it is not the term used to describe the specific action of comparing brands at different levels in a marketing research context